A flexible printed circuit board (FPC) is used in an electronic apparatus, such as a portable computer. The FPC comprises, for example, a base layer and covering layer laminated to each other. The base layer includes a base layer film and conductive layer laminated to each other with an adhesive. The covering layer includes a covering layer film laminated to the conductive layer with an adhesive.
The FPC comprises a rigid reinforcement plate configured for improved strength and easier component mounting and assembly. The reinforcement plate is affixed to a surface of the covering layer with an adhesive.
The covering layer film of the FPC is formed of, for example, hygroscopic polyimide. When the adhesive of the FPC is thermally set, therefore, water absorbed by the covering layer film is evaporated. The evaporated water may produce air bubbles between the reinforcement plate and covering layer. These air bubbles may cause the reinforcement plate to separate from the covering layer.